Processes for the electrochemical synthesis of organosilicon compounds are already known. For example, EP-A2 446 578 describes a process for the electrochemical preparation of polysilanes from halomonosilanes. DE-A1 40 24 600 discloses an electrochemical process for the preparation of carbosilanes and polycarbosilanes from (haloalkyl)halosilanes. P. Pons et al., describe, in J. Organomet. Chem. 358 (1988), 31, and in J. Organomet. Chem. 321 (1987), C27, an electrochemical process for forming Si-C bonds by reacting chlorosilanes with organohalogen compounds.
All these electrochemical processes have in common that during the electrochemical process undesirable by-products are formed which either adversely affect the course of the reaction or are difficult to dispose of. If, as described in DE-A1 4024600, an inert anode is used in the electrochemical process, when an electrode of this type is employed, the elemental halogen is formed on the anode side. In the case described there, elemental chlorine is formed. This may react with the supporting electrolyte, the solvent and/or the silane used. This reaction has the effect that the solvent is chlorinated (halogenated) and reacts with the silane, or that a carbanion/radical is formed at the cathode and reacts with the silane. Alternatively, it is possible for the supporting electrolyte to have a lower solubility in the chlorinated (halogenated)solvent, some of it precipitating, as a result of which the current flow in the electrolytic cell is reduced. A further possibility is that of the anode being passivated by the halogen, as a result of which the current flow in the electrolytic cell is reduced.
If the anode is a non-inert anode (sacrificial anode), the formation of elemental halogen is indeed prevented. However, metal halides are formed in the process which must be worked up and disposed of in an appropriate manner. If the metal halides are soluble in the system and are not adequately complexed, they may migrate to the cathode and there react instead of the halosilane, i.e., the current yield is reduced drastically.